1. Field of the Invention
The present invention relates to a plant cube, and in particular to a plant cube having a laminated structure of mineral wool fibres oriented in parallel to each other. The mineral wool fibres are predominantly formed into a coherent matrix and mutually bonded by a cured binding agent and, if appropriate, impregnated with a wetting agent for rapid water uptake before use. The mineral wool fibres may be stone wool fibres, glass fibres, Slag fibres and the like.
2. Description of the Prior Art
The air and water distribution within the growth cube is dependent on the hydraulic pressure over the height of the growth cube, but also is dependent on the internal surface value of the growth cube. The internal surface value is a function of the density of the growth cube, of the fibre diameter of the mineral wool fibres used and of the content of non-fibre material (shot).
Growth cubes have a total density within the ranges of 5-200 kg/m3, preferably between 20-180 kg/m3, more preferably 40-120 kg/m3, and practically 50-70 kg/m3. The fibre diameter is normally within the range of 1-20 micrometers, preferably 2-10 micrometers, such as 3-8 micrometers. The relative amount of shot varies between 0-50 wt % and typically is 0-40 wt %. For stone wool, the amount of shot is normally 30-35 wt %, and for glass wool the amount of shot is 5-10 wt %. Furthermore the aspect ratio for shot (ratio of length over diameter) is normally less than 5.
The value for the internal surface varies between 5,000 and 20,000 m2/m3. A high internal surface value is in the range of 16,000-20,000 m2/m3, a low value is in the range of 5,000-8,000 m2/m3 and a moderate value is in the range of 9,000-15,000 m2/m3.
An object of the invention is to provide new growth cubes which possess improved properties, such as better water distribution, better air distribution, better root penetration and distribution, and also better compression or bending strength.
New growth substrates have become available because of the use of a new technology for the production of growth substrates, that is, the provision of substrates comprising at least one layer of short tranversely extending fibres. Such a layer is produced by superfolding, in upward and downward directions, a web of mineral wool fibres. The fibres in the web are predominately horizontally oriented. The resulting product includes a folded or zigzagged structure positioned in a longitudinal direction formed from a layer of short transversely positioned mineral wool fibres. Each fold has a width in the range of 2-50 mm, preferably 4-40 mm or 2-40 mm.
The present invention provides a plant cube, comprising a laminated structure of parallel mineral wool fibres which impart the plant cube with better water spreading, water drainage, plant rooting and distribution. These features are dependent on the orientation of the mineral wool fibres in relation to the top and bottom surface.
Accordingly, the present invention includes a plant cube comprising a block of mineral fibres, having a top surface, a bottom surface and four side surfaces. The block comprises a laminated structure of parallel mineral wool fibres.
When the plant cube comprises substantially vertically oriented fibres, the plant cube provides improved water drainage, plant root penetration and distribution. Furthermore, less waste material is formed. Additionally, the plant cube has better contact with a slab on which the plant cube eventually is placed during outgrowth due to a better hydraulic contact. Furthermore, this plant cube is more coherent, rigid and stable.
In an alternative embodiment, the laminated structures comprise substantially horizontally oriented fibres. The resulting plant cube provides better water spreading. Therefore depending on the type of plant to be grown on the plant cube, either of the two plant cube types may be selected.
A third embodiment of the plant cube includes a pair of side layers of mineral wool fibres forming two mutually parallel side surfaces. The fibres of the side layers are oriented perpendicular to the fibres of the laminated structure. The resulting plant cube has high compression strength at the side layers which improves the form stability of the plant cube. A bottom surface of the plant cube may further define a groove between the side layers to provide additional strength.
When the laminated structure is subdivided into at least two substructures by a. division layer of mineral wool fibres oriented parallel to the fibres of the side surfaces, an optimum compression strength is obtained due to the presence of the division layer. Grooves may be defined in a bottom of the plant cube between each side layer and the division layer to provide additional strength.
When the bottom surface has a profile corresponding to a curing oven used to form the plant cube, the plant cube has a top surface which allows maximum penetration of water during dripping.
The effects of the plant cube according to the invention are maximized when the height of the side layers and the division layers is greater than that of the adjoining laminated structure.
The described benefits and other advantages and features of the plant cube according to the invention will be apparent from the following description of plant cubes according to the invention, which description should not be considered as limiting the scope of the invention.